不同土壤肥力条件下施氮量对小麦氮肥利用和土壤硝态氮含量的影响

Effects of nitrogen rate on nitrogen fertilizer use of winter wheat and content of soil nitrate-N under different fertility condition

在土壤肥力不同的两块高产田上,利用15N示踪技术,研究了高产条件下施氮量对冬小麦氮肥吸收利用、籽粒产量和品质的影响,及小麦生育期间土壤硝态氮含量的变化.结果表明：1.成熟期小麦植株积累的氮素73.32%～87.27%来自土壤,4.51%～9.40%来自基施氮肥,8.22%～17.28%来自追施氮肥;随施氮量增加,植株吸收的土壤氮量减少,吸收的肥料氮量和氮肥在土壤中的残留量显著增加,小麦对肥料氮的吸收率显著降低;小麦对基施氮肥的吸收量、吸收率和基施氮肥在土壤中的残留量、残留率均显著小于追施氮肥,基施氮肥的损失量和损失率显著大于追施氮肥;较高土壤肥力条件下,植株吸收更多的土壤氮素,吸收的肥料氮量较少,土壤中残留的肥料氮量和肥料氮的损失量较高,不同地块肥料氮吸收、残留和损失的差异主要表现在基施氮肥上.2.当施氮量为105 kg/hm2时,收获后0～100cm土体内未发现硝态氮大量累积,随施氮量增加,0～100cm土体内硝态氮含量显著增加;施氮量大于195 kg/hm^2时,小麦生育期间硝态氮呈明显的下移趋势,土壤肥力较高地块,硝态氮下移较早,下移层次深.3.随施氮量增加,小麦氮素吸收效率和氮素利用效率降低,适量施氮有利于提高成熟期小麦植株氮素积累量、籽粒产量和蛋白质含量;施氮量过高籽粒产量和蛋白质含量不再显著增加,甚至降低;较高土壤肥力条件下,获得最高籽粒产量和蛋白质含量所需施氮量较低.

Application of nitrogen （N） fertilizer is one of the most important measures that increase grain yield and improve grain quality of winter wheat （ Triticum aestivum L. ）. However, it is common that excessive N fertilizer is applied on high fertility field, which not only causes the decline of N use efficiency and economic effects, but also results in larger amount of nitrate-N accumulated in soil, and so it is concerned to bring potential risk to environment. This research was conducted to determine the effects of N fertilizer rate on N fertilizer use, grain yield and quality of winter wheat, and changes in soil nitrate-N content during wheat growth period under high-yielding conditions. The results will help to choose optimum N rate, to obtain profitable yields, efficient N use, and reduce the possible impact on environment. The experiments were carried out in two high-yielding fields, differed in soil fertility in Qianzhuliu, Longkou, Shandong,China, during 2002-2003. Seven N treatments （CK1, CK2, N1, N2, N3, N4, N5） were designed, with the N rate of 0, 0, 105, 150, 195,240, 285 kg/hm^2 ,respeetively. The N fertilizer was urea. Half of the N fertilizer was applied before sowing, and the other was topdressed at jointing stage. Apart from the treatment of CKI, all the other 6 treatments were supplied with 135 kg P2O5/hm^2 and 105 kg K2O/hm^2 before sowing. Each treatment had 3 replicates, with a plot of 3m×8m. In the field plots of N1, N3, N4 treatments, microplots of 15N traeing experiments were set, with the area of 15cm×44.5cm, and isolated with a 30cm high iron frame. Each 15N microplot had 2 replicates, which was added with 10.13 atom % 15 N-urea before sowing or topdressed. The rate and date of N application in the microplots were the same to these in the field plot. Wheat was sowed on Oetober 8 in 2002, with plant density of 120/m^2. The results showed that 73.32%-87.27 % N accumulated in wheat plant at mature stage was derived from soil, 4.51%-9.40% from basal N fertilizer, and 8.22%-17.28% from topdressed N fertilizer. With an increase of N fertilizer rate, soil N accumulated in wheat plant decreased, and fertilizer N that accumulated in wheat plant and remained in soft increased, whereas the recovery rate of fertilizer N decreased significantly. The amount of N that accumulated in wheat or remained in soil derived from basal fertilizer was less than that derived from topdressed fertilizer. The amount of N loss of basal fertilizer was more than that of topdressed fertilizer. Compared with the lower fertility field, the amount of soil N absorbed by wheat increased, whereas that of fertilizer N decreased, and the amount of fertilizer N remained in soil or became loss increased in the higher fertility field. The differences in plant uptake, soil residual and loss of fertilizer N between the two fields came mainly from those of the basal N fertilizer. With N application of 105 kg/hm^2 , no larger amount of nitrate-N was found accumulated in 0-100cm soil layers at mature stage. With N fertilizer rate increasing, the content of nitrate-N in 0-100 cm soil layers increased dramatically. With more than 195 kgN/hm2 was supplied, soil nitrate-N moved down obviously, and the upward nitrate-N movement occurred earlier and deeper in the higher fertility field than that in the lower one. With N fertilizer rate increasing, N uptake efficiency and N utilization efficiency of wheat decreased. With appropriate rate of N fertilizer added, grain yield, protein content and the amount of N accumulated in wheat plant all increased. High grain yield （ 〉 8800 kg/hm^2 ） and high protein content （ 〉 14.20% ） could be obtained in both the fields. However, with application of excessive N fertilizer, grain yield and protein content would increase little, and even decreased. The N fertilizer rates with the highest grain yield or the highest protein content in the higher fertility field were lower than that in the lower one. Based on analysis of grain yield, quality, N utilization and soil nitrate-N content, the N fertilizer rates recommended in the two fields were 105-150 kg/hm^2 and 150-195 kg/hm^2, respectively,